During discharging process of a lead acid battery, lead sulphate will form in electrolyte fluid of the battery. While during recharging process, the lead sulphate will be restored to lead and sulfuric acid. If the lead acid battery is always under the conditions of under-charging or over-discharging, lead sulphate deposition will crystallize and build up on electrical plates inside the battery. If the lead sulphate deposition is not dissolved for a long time, the deposition will accumulate on the electrical plates and form solid insulating points or layers thereon, which may affect the chemical reactions of active materials of the electrical plates, such as, lead, oxidized lead and so on. In addition, the lead sulphate would be not well-distributed in the electrolyte fluid during the course of charging or discharging of the battery, or as certain active materials in the electrolyte fluid will absorb the lead sulphate, the solubility of the lead sulphate will be reduced. Furthermore, with respect to a lead acid battery consisted of several internal cells connected in series, the internal cells may not be in equalizing state, and a weak or poor-conditioned cell among the internal cells will generate its own voltage level and will further deteriorate the condition of the battery.
If one or more of the above situations occur, the internal impedance of the lead acid battery will increase, the capacity of the battery will decrease or even lose, and the life thereof will be shortened.
Many methods and apparatuses proposed to de-sulphate lead acid batteries by applying charging pulses of different kinds thereon. However, it has been found that those methods and apparatuses were not always successful in rejuvenating weak lead acid batteries which are under the above-mentioned situations. The inventor of the present invention proposed a novel method and apparatus for rejuvenating a sulphated or weak lead acid battery by alternating two kinds of operations, which could not only dissolve the lead sulphate deposition on the electrical plates of the battery, but also bring the electrolyte fluid to a well-distributed and fully-restored state. In addition, the method and apparatus of the present invention could also efficiently equalize individual internal cells of the battery.